Hello all. I've recently upgraded my gaming computer and decided to make an emphasis on quietness. I have the Fractal Design Define XL r2 and I've replaced the 3 stock fans with Noctua NF-A14 PWM's (1x rear exhaust, 1x upper front intake, and 1x bottom intake). The Corsair RM850 is position with the fan facing down. My CPU cooling is the Noctua NH-D14 orientated to pull air from the front of the case and exhaust toward the rear exhaust fan. All of the moduvents are closed for silence.

Ultimately, the computer is EXTREMELY quiet from half a meter away (inaudible). This is assuming my case fans are running at 800 RPM (cannot get lower because of my mobo not having true PWM fan headers). If I max the intake fans and CPU fans, it becomes audible but bearable (1200 RPM w/L.N.A). Here is the problem I'm having: when the rear exhaust approaches 1000 RPM or higher, it creates a loud wind rushing noise which is very irritating. I'm in a 6ft x 10ft room with two desks and computers only - the noise seems to resonate through the wall behind my computer and I can hear it loudest from the opposite side of the room.

I'm very sensitive to sound and wondering if this is a normal phenomenon? I'm wondering if the pressure of the airflow is causing problems for a single exhaust? When I place my hand over the free-flow holes, I do not feel any suction or breeze. Should I reconfigure the fans, add more, or open moduvents? Thank you ahead of time for any help.

Personally i can hear the NF-A14 PWM over 650rpms, thats the top where i cant hear them, they are still quiet but over 900rpms they become very noticeable.

My suggestions, since you have 3 NF-A14 PWM, change them, see if you didn't get a defective. And if all do the same, then try 3 intake no out, the positive pressure and the NH-D14 should be enough to channel the air out through the holes of the back of the case and PCie covers.

Btw what motherboard do you own? most do have at least one true PWM fan header, and in this case you could just ran the NH-D14 fans on other headers since they are 3pin, and the 3 case fans with PWM splitter, the noctua will drop to 200rpms in the motherboard controls them via PWM, as long as the motherboard allows it.

This is assuming my case fans are running at 800 RPM (cannot get lower because of my mobo not having true PWM fan headers)

Yes, as already said the PWM fans are being run as 3 pin fans which is why the minimum speed is so high. I have used and would recommend the Akasa 5 way PWM splitter cable available from sources such as FrozenCPU. If your motherboard has an additional CPU PWM header (CPU_OPT on Asus and Gigabyte boards) you can run the splitter from there. The splitter cable draws the power for all the fans on the chain from a SATA connection, and distributes the fan control signal to all of them. The fans on the chain run in sync with the CPU fan, slow speeds at idle and only increasing rpm under system stress. One of the sockets on the chain (which should be marked as 'Master') will monitor the RPM of the fan connected to it. If you do have a CPU_OPT header and only want to run three fans on the chain the 3 way splitter could be used as shown below. All of these PWM splitter cables cost around $10 or less.

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